Considerable progress has been made in miniaturizing ground equipment designed to transmit signals to geostationary satellites. Such equipment is now commercially available and is known under the acronym "VSAT".
Civil telecommunications space network operators are finding that interference signals are being transmitted from unauthorized ground equipment fraudulently taking advantage of satellites operated by such operators.
Such interference signals are mixed with or even superimposed on the telecommunications signals normally received by the geostationary satellites of such space networks.
Situations are currently being encountered in which satellites in such space networks receive tens of interference signals in addition to legitimate signals.
As a result, the operators of such networks suffer considerable financial losses, and their customers suffer a reduction in transmission quality because of interference between the interference signals and the legitimate signals.
Therefore, operators currently need to eliminate or at least to reduce the number of such interference signals transmitted towards and to the geostationary satellites in their civil telecommunications space networks.
To this end, it is envisaged for each geostationary satellite to identify the arrival directions of the interference signals within the coverage zone of the satellite, so as to use the arrival directions to locate the ground equipment transmitting such interference signals, and then to have such equipment removed.
Systems are already known for identifying the arrival directions of signals arriving within the coverage zone of a satellite among legitimate other signals but with much higher power levels, i.e. about 20 dB to 25 db above the power levels of the legitimate other signals. In practice, the signals whose arrival directions are to be identified are distinguished from the other signals by their power levels.
Currently implemented known systems for identifying the arrival directions of signals are based on the use of sensors having overall coverage (isotropic over the coverage) installed on the satellite, the number of sensors to be provided depending on the number of signals whose arrival directions are to be identified. To identify the arrival directions of two signals, five sensors must be provided, and to identify the arrival directions of ten signals, twenty-one sensors must be provided.
Such a facility tends to become very complicated and bulky as soon as the number of sensors increases. Above about ten sensors in service, it is considered that the volume of calculations to be performed makes the facility too complex for it to be implemented in a payload on board a geostationary satellite.
In the current context, the interference signals generally have physical characteristics that are quite close to those of the legitimate telecommunications signals, and, in any event, not different enough from those of the legitimate signals to envisage distinguishing the interference signals on the basis of their power levels.